Load Calculation

ElectroBoard automatically calculates the load for every breaker and for the panel as a whole. This helps you check that ratings are chosen correctly, that the incoming supply is not overloaded, and that the phases are balanced.

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Consumers#

Any device with an outgoing cable (MCB, RCBO and others) can hold a list of consumers — the specific appliances or groups that this circuit feeds.

Each consumer is defined by:

• Name — what is connected (for example, "Water heater", "Kitchen sockets")
• Power — the power drawn, in watts
• Load type — sets the cos φ and the inrush factor
• Quantity — how many identical consumers are on this circuit

Load Types#

The load type automatically fills in the cos φ (power factor), the demand factor, and the inrush multiple:

Type	Examples	cos φ	Demand factor	Inrush
Resistive	Water heater, kettle, heater	1.0	1.0	1×
Motor	Motors, compressors, pumps	0.80	0.75	6×
LED (with PFC)	LED lamps with a driver	0.95	0.90	1×
Lighting (no PFC)	LED without PFC, fluorescent	0.65	0.90	1.5×
Heating	Underfloor heating, convectors	1.0	0.90	1×
Switching PSU	Computers, servers, chargers	0.70	0.80	3×
Mixed	General-purpose sockets	0.92	0.80	1.5×

cos φ affects the real current: at the same power, a load with cos φ = 0.8 draws 25% more current than one with cos φ = 1.0. Motor loads have a lower cos φ because of their inductive component.

The demand factor reduces a consumer's rated power down to what is actually drawn — sockets and lighting are rarely loaded to 100%. The default comes from the load type, but you can override it for each consumer (from 0.01 to 1.0).

The inrush factor is the ratio of starting current to running current: on switch-on, motors briefly draw 5–7 times their rated current (6× by default). This matters when choosing the breaker rating so that it does not trip on the inrush.

How Load Is Calculated#

For each breaker:

1. The power of all consumers is summed, taking quantity and demand factor into account
2. The current is derived using cos φ: single-phase I = P / (U × cos φ), three-phase I = P / (√3 × U × cos φ)
3. The result is compared against the breaker rating
4. Child-circuit loads are added to the parent breaker in a cascade — from the final groups up to the incomer

For the panel as a whole:

1. The loads of all root circuits are summed
2. The total power is shown in the toolbar as "∑ kW"
3. It is compared against the available capacity (if set)

Phase Balance#

For three-phase projects, ElectroBoard calculates the load on each phase separately and works out the imbalance percentage.

Imbalance formula: the largest deviation from the average, divided by the average, expressed as a percentage.

Imbalance	Rating	Action
Up to 15%	Fine	Everything is OK
15–30%	Noticeable	Redistribution recommended
Over 30%	Critical	Warning — move some consumers

The phase changeover helps to balance the load: it takes a three-phase input, but all of its child consumers run on a single chosen phase. By spreading consumers across several changeovers on different phases, you can even out the load.

Phase balance is shown in the toolbar as coloured L1, L2, L3 bars with the power in kW.

[screenshot: toolbar with phase balance and inlet utilisation indicator]

Inlet Utilisation#

If an available capacity is set in the project settings, the toolbar shows the inlet utilisation percentage:

• Up to 70% — normal (green)
• 70–90% — caution, approaching the limit (amber)
• Over 90% — overload (red)

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💡 Tip: Not all consumers run at the same time. Turn on the diversity factor (per IEC 61439-1) with the toolbar toggle, and the summed child-circuit load drops: 1.0 for a single circuit, 0.9 (2–3), 0.8 (4–5), 0.7 (6–9), 0.6 (10–40), 0.5 (over 40). See more in the Automatic Checks section.

Implicit Neutral Consumers#

A single-pole breaker (1P) without an N pole does not physically switch the neutral, but its 230 V load circuit still needs a neutral. ElectroBoard automatically accounts for such devices when working out how many terminals the neutral bar (N) requires.

This means that even if a 1P breaker is not wired to the N bar explicitly, the tool correctly sizes the N bar for the whole group — taking into account every 230 V consumer under that parent device.